Every year, tens of thousands of fans make the pilgrimage to Bristol Motor Speedway to watch some of the biggest superstitions in auto racing. But just how much dirt was actually put down at the famous Virginia track?
It depends on which day you ask. But on some days, a lot more dirt was put down than others. Here’s a look at some of the variables that might affect the amount of soil that ends up being covered by a racing car during a typical NASCAR race weekend.
Rainfall And Winds
There are two factors that can affect how much dirt gets covered during a race: rainfall and winds. While it rained heavily throughout the entire Bristol weekend, the heaviest downpour of the entire season, the 2019 race saw the track nearly dry. With the exception of the final race on Sunday, most of the races saw less than an inch of rainfall. And even that was mostly in the form of mist. However, extremely high winds made it difficult for the grounds crew to keep up with the track surface, creating ruts and bumps that nagged at the cars all season long. It was particularly noticeable in the Daytona and Phoenix 600s, which were run under severe wind conditions. This is one of the reasons why those two races saw significantly more dirt surface exposure than average. (And if you’re curious, the average amount of dirt on a Bristol weekend is 54.3 inches.)
Track Surface Temperature
Track surface temperature is also a major factor in how much dirt gets covered during a race. The hotter the track, the more dirt that will be removed during each service interval. The surface temperature of Bristol is usually in the mid-80s during the day and in the high 70s at night, which makes it a bit more moist than other tracks. The increased humidity causes the surface to grow slick and sticky due to the temperature gradient, which then makes it more susceptible to rutting. As a general rule, the hotter the track, the more bumps and ruts you will see. (The exception to this rule is when it’s very cold and damp out, in which case less dirt is needed to keep the track surfaces at their optimum consistency.)
Wet Weather Vs. Dry Weather
The key phrase to keep in mind when it comes to dirt surfaces is “wet weather vs. dry weather.” While the track may look dry, it really depends on how long the precipitation has continued. If there’s been any at all, then it’s wet weather, and if the precipitation has stopped then it becomes dry weather. Sometimes, a heavy downpour of rain will wash away all the dirt covering the track and turn it into a pure, smooth sheet of blacktop. This is almost always the case at a few select tracks, such as Daytona and Talladega, where it never stops raining. At other tracks, like Bristol, the downpours of rain will be more of a sprinkle than a downpour, allowing for more gradual and gradual changes in surface conditions. This is one of the reasons why only certain races at Bristol require more surface preparation than others. (The average amount of dirt on Bristol during the 2019 season was 55.9 inches, with the lightest amount being 52.3 inches in the April 15th race and the heaviest amount being 65.6 inches in the July 19th race.)
If there are no wet conditions then it’s simply a matter of keeping the track surface free of as much water and mud as possible. This can be achieved through a combination of careful preparation and spotty rainfall. During the off-season, track workers will strip the track of all loose dirt and brush, removing any excess overhanging vegetation. This leaves the track looking clean and neat, but also allows for more aerodynamic car designs and lower drag levels, which translate to faster speeds and more exciting racing. (The most recent addition to the Bristol track surface is the tri-oval, which was built following the 2018 season. Prior to its renovation, the track layout was similar to a traditional oval, with two straightaways and a long back-straightway connecting them. The renovation allowed for a smoother transition between the different configurations, as well as eliminated the need to cross the track once the layout was changed. This made it more convenient for spectators and participants alike.)
The temperature at which the track surface is maintained also determines how much dirt is needed to maintain its condition. The optimum temperature for most dirt surfaces ranges from 60 to 80 degrees Fahrenheit. Anything above 80 degrees and the road will become dangerous as the asphalt will start to break down, resulting in potholes, buckling and blockage. Below 60 degrees, the road will become a slippery mess of mud and water, which not only makes it difficult for cars to handle, but also presents a danger to drivers and vehicles alike. Therefore, it’s best to keep the track surface at a steady 60 to 75 degrees, except when it’s very wet and cold, then you can drop it down to 50 degrees to save the asphalt and the cars.
The frequency of service intervals is also a factor in how much dirt is needed at any particular track. The difference is that some tracks, like Bristol, require more frequent services than others. The frequency of service depends on a number of variables, including the type and make of the car, the track surface temperature and whether it’s wet or dry outside. (The average service interval for a NASCAR race is about 10 or 11 minutes. Drivers change four or five tires during that time, which means that they’re constantly having to stop and exit the vehicle to make adjustments and check tires. The need for frequent services is one of the main reasons why cars wear out more quickly on average at Bristol than at other tracks, like Talladega, where there are fewer extreme conditions and the service intervals are longer.)
Types Of Dirt
There are also several different types of dirt that are used at different tracks, which again, can affect how much dirt ends up being covered during a typical race. Most tracks use a mixture of clay, sand and pebbles in their dirt, along with a small amount of water. The mixture is compacted to make a smooth, level surface that’s then sprayed with water to make it more abrasive and grippy. The clay in the dirt improves traction while the sand makes the surface harder, which leads to faster speeds. The water also makes the surface more environmentally sustainable as it reduces the dust that’s raised by tire wear. (The least expensive option for track grounds crews is used motor oil, which can be quite the sticky mess when mixed with water and road debris. Thankfully, it’s easily cleaned off and doesn’t pose a threat to the environment. But it could be considered a nuisance aside from that fact, especially for the track workers and drivers who need to cleanse their vehicle interiors before entering them following a particular race. On average, Bristol tracks use about 18 gallons of motor oil per day, but the amount can vary depending on the track surface conditions. (The average amount of gas at the track during the season is 3.2 gallons per day. This is also the case at Daytona and Talladega, which means those are some pretty expensive racetracks if you decide to drive there a lot during the year.)
As mentioned above, the amount of rain that falls at a particular track can vary from year to year and from one weekend to the next. Some of the heaviest rainfall is typically associated with hurricanes and/or powerful storms that move through the area. The 2019 Atlantic Hurricane Season was exceptionally active, with 13 named storms and six major hurricanes. On September 1st, a hurricane named Dorian made landfall in North Carolina and remained there for nearly a week, during which it ripped through the Outer Banks, causing billions of dollars in damage and leaving a trail of death and destruction.
While some NASCAR fans and participants in the Atlantic Coast Conference will be able to enjoy the nostalgic appeal of a half-dozen hurricanes ripping through the area during the season, the damage left in their wake will be anything but nostalgic.
The 2019 season also saw the United Kingdom suffer through its summer of hell, as the country saw some of its worst floods for centuries. The heaviest rainfall was in the south-west, with some areas receiving over two feet of rainfall in a matter of days. This caused widespread devastation, with approximately 70 people known to have died as a direct result of the flooding. While the impact in the UK was significant, one could argue that it wasn’t as bad as it could have been, due to the overall resilience of the country.